I recently watched this excellent video on keeping nucs as part of one's operation. It's long so that means if I'm recommending it, it's really good. This is just part one, there's also a part two.
Mike Palmer 4/2011 The Sustainable Apiary Part 1 of 2 from PWRBA (Prince William Regional B on Vimeo.
The idea is that keeping nucs, even as many as you have regular hives gives you all sorts of flexibility and sustainability in your bee yard especially if you are raising your own queens. At this point in history, any serious beekeeper should. As Michael explains, queens and packages are becoming more and more unreliable.
Among other reasons, nucs offer the ability for quick requeening, quick hive replacement, quick increase, the ability to use a nuc as a 'bee bomb' to boost a hive's production, the ability to raise and test queens before devoting much equipment to them, the ability to draw out new combs rapidly without suffering honey production, and as a consistent product to sell.
I currently have the equivalent of 10 nucs that I will be attempting to put into circulation this next spring. After this disastrous summer we've just had, the idea of selling nucs primarily appeals to me as such a thing can be done even with zero honey production in a calendar year. The really big thing that I learned was not to make nucs from your big productive hives, but to make nucs from mediocre healthy hives, but make queens from your big productive hives. Thus far, I have been splitting queens the old Emergency Queen way but this next year, I'm going to be grafting. If that fails, I'll try the Nicot system or Jenter.
I could go through and explain the whole system to you but it would take hours to type and read and you can watch the whole video yourself. So please go watch the video. You'll find it well worth your time.